Molecular oxygen observed by direct photoproduction from carbon dioxide

Abstract

Oxygen (O2 ) is one of the most important elements required to sustain life. The concentration of O2 on Earth has been accumulated over millions of years and has a direct connection with that of CO2 . Further, CO2 plays an important role in many other planetary atmospheres. Therefore, molecular reactions involving CO2 are critical for studying the atmospheres of such planets. Existing studies on the dissociation of CO2 are exclusively focused on the C-O bond breakage. Here we report first experiments on the direct observation of molecular Oxygen formation from CO2 in strong laser fields with a reaction microscope. Our accompanying simulations suggest that CO2 molecules may undergo bending motion during and after strong-field ionization which supports the molecular Oxygen formation process. The observation of the molecular Oxygen formation from CO2 may trigger further experimental and theoretical studies on such processes with laser pulses, and provide hints in studies of the O2 and O + 2 abundance in CO2 -dominated planetary atmospheres.PACS numbers: 33.80. Gj, 42.50.Hz, O 2 production is one of the most important processes for the biosphere of the Earth.Oxygen molecules are mainly generated via the photosynthesis by green plants and algae from carbon dioxide and water:. CO 2 is not only important for the atmosphere on Earth, it is also the dominant compound of the atmosphere on other planets, such as Mars and Venus. One of the most crucial tasks for the quest to establish a human settlement on Mars is the production of O 2 [2]. Because more than 95% of the atmosphere on Mars is CO 2 , it will be extremely helpful if O 2 can be produced directly from CO 2 . In the past, it was observed that dissociation of CO 2 via absorption of photons leads to carbon monoxide (CO) and oxygen atoms (O) [3]. However, theoretical simulations suggested the possibility of generating O 2 through the dissociation of a CO 2 molecule [4]. A recent experiment showed the evidence of O 2 formation from CO 2 molecules after UV excitation through the detection of C + [5]. So far, O 2 formation from CO 2 has not been directly observed.In the past decade, intense ultrashort laser pulses have been successfully applied to trigger and control molecular reactions such as dissociation and isomerization [6][7][8][9][10][11][12][13][14][15]. When a molecule interacts with a strong laser field, electrons from outer molecular orbitals can be excited or removed through tunneling or over-the-barrier ionization which may prepare the molecule in an excited state or a state with a certain charge. As a consequence, the excited or ionized molecule may undergo severe geometrical reconfiguration and may also break into several fragments or form new chemical bonds. Because of the importance of CO 2 in many research disciplines, strongfield induced reactions of CO 2 have been experimentally studied with ultrashort lasers by several research groups.However, these studies mainly focused on the topic of ionization and dissociation [16]. In this paper, for the first...

Ion-ion coincidence imaging at high event rate using an in-vacuum pixel detector

“…7(b). The same finding was recently reported by Larimian et al 30 on the basis of COLTRIMS measurements. However, in contrast with the results presented there, our data do not show any evidence for a slow dissociation pathway into C + + O 2 + ion analogous to the previously discussed dissociation into O + + CO + (see Figs.…”

“…9 exhibits a 2 eV broad peak centered around 5.5 eV and agrees with previous work. 26,30 In addition to the two O + + CO + pathways, the ion-ion coincidence map reveals a number of additional pathways. into CO + + O + .…”

Direct dioxygen evolution in collisions of carbon dioxide with surfaces

“…Although inaccessible by thermal activation, transitions to electronically excited and anionic states of CO 2 can bend the molecule as a first step to O 2 production. Indeed, pioneering experiments employing VUV photo-excitation 14–16 and electron attachment 17,18 have shown that dissociation of CO 2 into C( 3 P) + O 2 (X 3 Σ g − ) is possible, as evidenced by the detection of the complementary atomic C + or C − fragment. Further confirmation of the exotic pathway, however, remained elusive as neutral or ionized O 2 products were not detected.…”

Strong-field-induced bond rearrangement in triatomic molecules

“…Examples of such processes include roaming [4,10,13,17,19,24], in which a neutral moiety traverses the molecule to capture another atom, hydrogen migration [9,12,15,16,18,20,21,25] and bond rearrangement [1, 3, 5-8, 11, 14, 22, 23, 28, 30], in which the cleaving of multiple bonds initiates a process leading to the formation of a new molecule from atoms that were not previously bonded to each other. A number of prominent photochemical reactions involve these processes, including decomposition of water [31] or NO 3 [32,33] by photolysis, the conversion of carbon dioxide to oxygen in the atmosphere [26,34], the combustion of hydrocarbons [12,15,20,25] and the formation of H + 3 from alcohols [10,24]. In addition, there is expanding interest in moving beyond observing the dynamics of these processes to controlling those dynamics using ultrafast lasers (see, for example, Refs.…”

“…Despite the increasing attention devoted to these processes, so far most studies have focused on a single molecular species and have occurred under an assortment of experimental conditions. For example, the initiating ioniza-tion mechanism in previous bond rearrangement studies has variously included single [8,11,[37][38][39][40][41][42] and multiple photons [5,22,26,27,43] as well as electron [23,28,44] and heavy ion impact [2,7,30]. To assist in understanding these dynamics we examine bond rearrangement following ultrafast strong-field double ionization of three triatomic molecules: carbon dioxide, carbonyl sulfide and water.…”